Project Summary/Abstract Osteoporosis has become a major and growing worldwide public health burden. Due to fears of side effects, the use of osteoporosis drugs has fallen by as much as 50%. Thus, there is an unmet need to develop new drugs for osteoporosis; or to develop personalized therapeutic approaches with the ability to takes into account individual variability for each patient. Using human genetic studies to identify new druggable targets should overcome the current treatment crisis in osteoporosis. Although GWAS have been successful in discovering associated genetic variants with complex traits, more than 88% of GWAS loci are non-coding, which makes the identification of causal variants and their targeted genes a difficult challenge; thus, limits the use of human genetics information in drug discovery. To overcome these challenges and get better understanding of GWAS findings, we proposed to utilize whole genome sequencing in large well-phenotyped populations as well as the CRISPR/Cas9 gene-editing zebrafish model to identify potential causal variants and targeted genes influencing skeletal integrity. Our findings may eventually lead to new diagnostics and therapeutics of osteoporosis. We proposed three specific aims, including: 1) Fine-map previous BMD GWAS loci by existing WGS in 10,000 individuals from the Trans-Omics for Precision Medicine (TOPMed) Program to identify potential causal sequence variants (functional variants) that are responsible for GWAS signals; 2) Identify novel structural variation and novel rare sequence variants associated with BMD by performing a whole genome scan using the same 10,000 WGS samples. We will replicate findings in an additional 5,000 samples selected from the GENOMOS/GEFOS consortium; 3) Functionally characterize up to 30 genes selected from aims 1 and 2 in knockout zebrafish by CRISPR/Cas9 gene-editing systems. State-of-the-art technologies for rapid phenotyping in zebrafish will be applied to a broad range of physiologies (skeletal development, ontogenesis, and regeneration) and characteristics (bone mass accrual, morphology, and mineral density). Our proposal is fundamentally important and represents the logical next step in skeletal genetics research. The results will lead to much needed new drug development to overcome the growing treatment gap in osteoporosis.